EP3204738A1

EP3204738A1 - Optical filter element for devices for converting spectral information into location information

Info

Publication number: EP3204738A1
Application number: EP15797588.9A
Authority: EP
Inventors: Maik LANGNER; Hartmut FRÖB; Vadim G. LYSSENKO; Markas Sudzius; Karl Leo
Original assignee: Technische Universitaet Dresden
Current assignee: Senorics GmbH
Priority date: 2014-10-07
Filing date: 2015-10-07
Publication date: 2017-08-16
Anticipated expiration: 2035-10-07
Also published as: US10012541B2; ES2799427T3; CN107110705A; WO2016055048A1; DE102014014983A1; CN107110705B; EP3204738B1; DE112015004604A5; US20170241838A1

Abstract

The invention relates to an optical filter element (50) for devices (70) for converting spectral information into location information, using a connected detector (30) for detecting signals, said element having at least two microresonators (10, 11), a microresonator (10; 11) at least comprising - at least two superposed reflective layer structures (4, 6; 8, 9) which consist at least of a material layer (2) having a high refractive index and a material layer (3) having a low refractive index in an alternating sequence, as well as - at least one superposed resonance layer (5; 7) which is arranged between said two superposed reflective layer structures (4, 6; 8, 9). The filter element (50) comprises at least one transparent plane-parallel substrate (1) for optically decoupling said two microresonators (10, 11), the first microresonator (10; 11) being located on a first of the two opposing surfaces (51; 52) of said substrate (1), and the second microresonator (11; 10) being located on said substrate (1) on a second surface (54) thereof (1) that lies opposite the first surface (51), the resonance layer (5; 7) of at least one microresonator (10; 11), and/or the reflective layer structure (4, 6; 8, 9) that surrounds said resonance layer (5; 7), having a layer thickness which can vary along a horizontal axis (25) of said filter element (50).

Description

Technical University Dresden

Helmholtzstraße 10

01069 Dresden

Optical filter unit for facilities for the conversion of spectral

Information in location information

The invention relates to an optical filter element for devices for the conversion of spectral information into location information with an activated detector for detecting signals,

at least comprising two microresonators,

wherein a microresonator has at least

= at least two area-covering reflective layer structures at least from a material layer with a high refractive index and at least one material layer with a low refractive index in an alternating sequence as well as

- At least one area-covering resonance layer, which is arranged between the respective two area-covering reflective layer structures. State of the art

For the spectral analysis of optical signals, a separation into individual wavelengths is necessary, which are subsequently converted into an electrically utilizable data stream for evaluation by means of signal converters. This is done by converting the spectral information into a location information. Heretofore, diffractive / refractive elements (optical gratings, prisms) have been used for this purpose, which have to have a sufficient geometric extension for a high spectral resolution (i.e., sufficiently long splitting of the incident light). In addition, the mutual alignment of the optical elements must be thermally and mechanically stable enough to avoid systematic errors in the measurement. Thus, previous spectrometers are not suitable for all locations, or the cost of the application are too high.

The technical development of spectrometers has led in recent years to miniaturization and cost reduction. Current devices fit on a palm (for example: USB spectrometer) and still achieve a sufficient resolution (»1 nm FWHM) and an acceptable signal-to-noise ratio (1: 1000). The basic principle of the measurement has not changed significantly. Via an optical system (for example: lens system, optical fiber) and an entrance slit, the input signal is projected onto a dispersive element. Typically, prisms or grids are used. The spectrally separated signal from the dispersive element is then directed to a detector whose signals can then be further processed. In order for the separated signal to be resolved by the individual elements of the detector, the signal path has a length dependent on the deflection angle of the disperse element. The length can not be arbitrarily shortened, whereby spectrometers on this basis have a minimum extent.

An alternative implementation of a spectrometer involves the use of a bandpass filter with locally variable filter characteristics together with a Detector unit. The filter elements described in the document US Pat. No. 6,057,925 A under the term LVF "linearly variable filter" are based on interference effects and typically consist of a layer system of metallic and / or dielectric thin layers which are technically applied to a substrate such that the layer thicknesses and The individual components of the input signal are thus attenuated to different extents, depending on the location, and the calibration of the position of the active detector elements allows the spectral information to be obtained spectrally resolving and measuring component of the component are made particularly compact and robust.

However, the utilization of the interference effect for the separation of the light has the consequence that the filter has a directional dependence of the incident signal. The farther away the angle of incidence is from the vertical entrance of light, the more the spectral filter characteristics shift to shorter wavelengths. As a result, a clear correlation between the active detector element and the filtered wavelength is no longer given and the practical spectral resolution deteriorates markedly compared to the theoretically possible (defined by filter characteristic and detector resolution). To avoid this directional effect, the input signal must be optically adjusted before / during the passage through the device to be within a narrow angular range. in the document US 6,785,002 B2 "Variable filter-based optical spectrometer" or in the document US 2004/032584 A "Optical Channel monitoring device" is the basic structure and operation of such an integrated system for use in telecommunications under splitting ge - multiplexed signals set forth. The light coupled out of an optical fiber strikes a lens system and is then projected onto the filter element in a collimated manner. The individual spectral components are then detected via the sensor located behind. For a high resolution, the Use of an etalon with dielectric mirrors proposed for the variable filter element.

The document US 2003/058447 A1 "Colorimeter apparatus for color printer ink" describes a component in which the directional selection takes place via a matrix of glass fibers or a flat collimator arrangement between the detector and the filter Collimator can be used on the inlet side of the filter.

As a further variant for limiting the direction of the incident signals, self-focusing lens arrays should also be mentioned at this point, as described by way of example in US 2010/092083 A1 "In-line linear filter based spectrophotometer".

A further variant of the spectroscopy by means of linearly variable filters is described in US Pat. No. 5,144,498 A. "A variable wavelength light filter and sensor system." In this case, incident light is reflected by reflection on up to two variable filters onto an optional third filter element and subsequently In this configuration, the filters may also be on the side surfaces of an equilateral prism.

A disadvantage of the above-mentioned solutions is the fact that a partially spatially extended optics or an additional complex component to be manufactured is necessary in order to obtain useful spectroscopic information from the combination of variable bandpass filter and detector.

US 2007/0148760 A1 describes a method for detecting chemicals and biomolecules, which consists of the following steps:

Generating light from a light source, Incidence of light on / in an optical sensor emitting a narrow band of optical wavelengths when illuminated with a wide band of optical wavelengths,

Spreading the exit light from the sensor to a detector having an entrance surface comprising at least / at least one layer with a laterally variable transmission property, and

- Using the position of the exit light by means of the detector to detect the presence of an analytic (chemical or biomolecules). The associated facility includes

a light source producing a wide band of optical wavelengths,

an optical sensor which outputs a narrow band of optical wavelengths when illuminated with a wide band of optical wavelengths from the light source,

a detector comprising at least one layer of laterally varying transmission characteristics while the detector receives exit light through the optical sensor, at least one layer transmitting a portion of the received light at a position of the at least one layer and the detector utilizing the position to grasp the presence of the analytic.

Furthermore, US 2007/0148760 A1 describes a method for obtaining information about an analytical agent, the method comprising:

Generating an excitation of an analytic on an analyte-to-wavelength converter in relation to the transducer producing an exit light, the exit light indicating analytic information;

Propagating the exit light to an entrance surface of a transmission structure, the transmission structure having an exit surface comprising a set of two or more positions, the transmission structure being a layered structure having a laterally variable energy transmission function, and Passing the exit light through the transmission structure to an exit surface such that relative amounts of photons produce a set of positions, the relative amounts indicative of analytic information.

The associated facility includes

an analyte-to-wavelength converter responsive to an analytic stimulus by generating an exit light indicative of analytic information, a transmission structure having an entrance surface and an exit surface, the exit surface comprising a set of at least two positions, the transmission structure being a layered one Structure with a laterally variable energy transmission function is, and

a propagation component directing the exit light from the transducer to the entrance surface of the transmission structure with respect to the exit light, the transmission structure generates photons on the set of exit surface locations such that the relative amounts of the photons produce a set of positions, the analytic Display information.

A disadvantage of the latter two solutions is that the light signal to be analyzed must be aligned as parallel as possible for a good resolution before the impact. These additional optical components, such as. Lenses or blades (blades) are necessary.

US Pat. No. 6,768,097 B1 describes an optoelectronic device in which a coupling of two microresonators, which are arranged at a distance from one another, is used to filter wavelengths. In this case, a first microresonator has a comparatively large extent (a few 100 μm), which results in a large number of resonances, referred to as the frequency comb. In contrast to the former, the second microresonator has an extent of the order of its resonance wavelengths. In addition, the resonant layer of the second (thin) microresonator is electrically controllable to change its optical properties (thickness, refractive index). This makes it possible to filter out one of the resonances of the frequency comb.

On the one hand, the disadvantage is that the frequency comb of the first microresonator does not permit a continuous spectrum during the measurement. Furthermore, an electrical drive is necessary for the selection of the signal transmitted through both micro-resonators. Thus, another disadvantage is apparent, with a measurement of a broad spectrum is necessary only in series, whereby the temporal resolution is limited.

task

The invention has for its object to provide an optical filter element for facilities for the conversion of spectral information in Ortsinformatio- NEN, which is designed so suitable that the structure in facilities for spectroscopy or spectrometry is space-saving in alignment of the light signal and thereby formed inexpensively.

description

The object of the invention is achieved by means of the features of patent claim 1.

The optical filter element for devices for the conversion of spectral information into location information with an activated detector for the detection of signals

includes at least two microresonators,

wherein a microresonator has at least

at least two full-coverage reflective layer structures at least of a material layer with a high refractive index and at least one material layer with a low refractive index in an alternating sequence as well as at least one area-wide resonance layer, which is arranged between the respective two area-covering reflective layer structures,

wherein according to the characterizing part of patent claim 1

at least the filter element comprises

a transparent, plane-parallel substrate for optical decoupling of the two microresonators,

wherein the first microresonator is located on a first of the two opposite surfaces of the substrate,

wherein the second microresonator is located on the substrate on a second surface of the substrate opposite the first surface, and

wherein the resonance layer of at least one microresonator and / or the respective reflective layer structure surrounding the resonance layer have a variable layer thickness along a horizontal axis of the filter element.

The devices preferably represent spectroscopic / spectrometric devices.

As an optical filter element in the context of the invention, structures are referred to which interact with the photons when introduced into a light path in such a way that a measurable fraction of the photons is missing after passing through the filter. According to the invention, only a spectrally narrow band passes through the filter element, while the remaining spectrum is completely reflected or absorbed in the structure.

As spectrometric or spectroscopic applications within the meaning of the inventions methods and devices are referred to, in which radiation is decomposed and an assignment of a spectral parameter (wavelength, intensity) is given to a readable detector element. Conversion of spectral information into location information in the sense of the invention designates the mode of operation of the filter element in such a way that the light strikes the filter over its entire area and, after the passage, separates the individual spectral components over its spatial extent, depending on their construction.

As a detector according to the invention optoelectronic sensors are referred to, in which photons is converted by the photoelectric effect into an electrical signal. These include, for example, photocells, photomultipliers or CMOS / CCD elements and photodiodes.

According to the invention, the detector includes a number of individual sensor elements, for example pronounced as a row or matrix. The individual elements can be equipped with diverging shape / size and spectral sensitivity.

As a signal within the meaning of the invention, electromagnetic radiation is referred to, which strikes both monochromatically (one frequency / wavelength) or spectrally broadband on the filter. In this case, the signal may have a temporal intensity modulation (single pulse, periodic and aperiodic variation), or occur with a constant intensity distribution.

As a microresonator in the context of the invention, a component is referred to, which interacts with electromagnetic radiation such that standing waves can form inside (resonant layer). For this purpose, its walls are designed as boundary surfaces (partially) reflective.

It is essential that at least one spatial direction has an extent in the order of magnitude of the spectral range to be examined, for example for light of a few 10 nm to a few pm. For the considered filter element, this spatial direction is perpendicular to the expansion surface of the films / surfaces of the substrate.

According to the invention, a nationwide pronounced layer structure designates a sequence of interconnected material layers (eg: metal oxides, metals, polymers, organic molecules, etc.) which each have a surface extension of a few mm ² to several 100 cm ² and a thickness in the order of less than 10 nm to several 100 nm, wherein between each two materials exactly one interface arises, the extent of which deviates insignificantly from it. The successive interfaces in a structure with more than two layers are parallel to each other in one dimension. Due to the size ratio of their dimensions, the layers are also referred to as films.

Fabrication methods for these films are prior art methods such as vacuum sublimation, sputtering, spin coating, dipping methods. Reflective in the sense of the invention are highly reflective photonic structures, also referred to as dielectric mirror, in the interference effects over a high proportion of radiation (nearly 100%) within a spectrally wide band (some 10nm - some 100nm) is completely reflected. In contrast to metallic mirrors, the efficiency is almost 100%, since usually no or almost no radiation is absorbed. A simply designed dielectric mirror consists of an alternating sequence of layers of transparent materials for the considered wavelength range, which differ from one another in their respective refractive index. In the visible spectrum these would be, for example, the materials silicon dioxide (n_Si02 = 1.46) and titanium dioxide (n_Ti02 = 2.4-2.6), which are each set to an optical thickness nxd of one fourth of the maximum wavelength to be reflected. With a number of about 7-9 alternating pairs of layers, reflection values> 99% can be obtained. For adaptations of the specific reflection behavior in a broad spectral range of several 100 nm, additional layers or layer stacks with precisely calculated layer thickness deviations can be added. Variable layer thickness in the sense of the invention designates a specifically set profile of the thickness along a horizontal axis in which the layers are expanded in a planar manner. This profile may have discrete levels, or change continuously. A possible expression is a wedge shape, for example for the resonance layer, in which there is a layer thickness increase of 10 nm -20 nm per mm in the horizontal direction. The lower the variation per unit length, the greater the spectral resolution can be, or the sensitivity when using larger detectors, on the other hand, thereby increasing the horizontal extent at a constant measuring range.

Manufacturing methods for variable layer thicknesses include i.a. Immersion method with time-varying immersion depth, vapor-deposited or sputtered layers at an angle, alternatively time-variable apertures, which shield a source. The apertures may periodically (e.g., rotate) inhomogeneously cover the growing layer, as well as progressively cover from the beginning to the end of the deposition.

At least a portion of the reflective layer structure and / or at least one resonant layer may be made of a dielectric material.

At least one of the reflective layer structures may consist of a layer stack of alternating high-index and low-refractive optically transparent materials. At least one resonant mode of the microresonators has a transmittance higher than 10%, preferably higher than 50%, particularly preferably higher than 90%.

The geometric structure and / or the material composition of both micro-resonators can be symmetrical to the substrate plane. In the case of the filter element, the layer thickness profile of the reflective layers along a horizontal axis of the component or filter element may be related to the course of the resonant layer thickness. The first resonant layer of the first microresonator may consist of a dielectric material different from the second resonant layer of the second microresonator, and thus the resonant mode (s) may have a dispersion parabola having mutually different curvatures. The extent of the surface of the substrate may be relatively small perpendicular to the slice gradient direction.

In the direction of radiation elongated, absorptive wall elements may be attached to the sides of the filter element.

A locally variable optical filter part may be arranged in front of the one of the microresonators in which a spectral preselection of the incoming signal takes place by means of absorptive, transmittive or reflective bandpasses. A spectroscopic / spectrometric device for converting spectral information into location information comprises at least

a light source,

a detector,

an evaluation unit which is connected to the detector via a connecting line,

a display unit and

an aforementioned filter element according to the invention,

wherein according to the characterizing part of patent claim 11

the filter element is designed such

that it transmits a short-wave component of the light from the light source after passing through the filter element in the short-wave transparent region and a long-wave component of the light from the light source after passing through the filter element in the long-wave transparent region and that it reflects a long-wave component of the light of the light source after hitting the filter element in the short-wave transparent region and a short-wave component of the light of the light source after hitting the filter element in the long-wave transparent region.

The spectroscopic / spectrometric device may have as a detector a photoelectric series / matrix converter based on CCD, photodiode or multiplier. The bandpass filter of the filter element according to the invention is designed so that a collimation takes place within the filter element and no further optical elements are needed. This makes it possible to realize particularly compact and inexpensive spectroscopic components or devices. In summary, the following can be stated.

In front of a detector (CCD matrix, diode array, array), the optical filter element according to the invention is attached as a spectral (linear) graduated filter. The gradient filter advantageously consists of at least one photonic crystal with a location-dependent variable layer thickness of at least one layer. The gradient filter reflects in a spectrally wide band all incident optical signals except for a structure-dependent and position-dependent specific resonance. The non-reflected narrow spectral range (<1 nm possible) passes through the filter almost unhindered and can then be converted into an electrical signal in the immediately downstream detector.

The invention thus relates to an optical filter element for separating the electromagnetic spectrum in the UV to IR range, which in combination with a downstream signal converter makes it possible to decompose an electromagnetic broadband signal into its individual components (spectroscopy, spectrophotometry). In the present invention, no upstream optical elements are necessary for signal shaping, whereby a compact integrated element can be realized. For the separation of the electromagnetic signal into its individual components, an arrangement of at least two variable miroresonators is used, which are located opposite one another on the respective surface of a transparent plane-parallel substrate.

If Fabry-Perot interferometers are used for the variable optical micro-resonators, a good to very good signal-to-noise ratio can be achieved at high spectral resolution at the same time. By adapting the parameters of the filter element, on the one hand the spectral width and the position of the measuring range, a high directional sensitivity or a very high individual signal separation can be achieved. At the same time, the compact construction of the filter element makes it possible to integrate it into a large number of processes previously inaccessible for optical spectroscopy. For the production of the filter element, methods known from the prior art for the production of thin-layer systems can be used, which include, among others, both vacuum coating (PVD, CVD) and sol-gel processes.

The key point of the optical filter element is in addition to the transparent substrate variable bandpass filter. In this context, the term optical filter element designates a component which, upon irradiation with an arbitrarily spectrally composed electromagnetic signal in the wavelength range of 100 nm-10 pm (UV-IR), reflects or transmits parts of the spectrally combined electromagnetic signal to different degrees, optionally also absorbed. The signal component is determined by the specific structure of the filter element and can include spectral bands from sub-nm to several 100 nm width (bandpass / band stop), but also hide individual regions of the optical spectrum (for example: transmission of short wavelengths using a shortpass).

In the presented invention, a substrate is used which has a sufficient transparency greater than 25% for the desired wavelength range to be investigated. For example, solid materials such as glass in the UV / VIS range or silicon in the IR range can be used as materials, but also plastics or equivalent polymers can be used. The sub strat generally has a surface extension of a few millimeters to a few centimeters edge length. The thickness as the third variable is a decisive parameter for the function of the filter element according to the invention and is between a few 1/10 to a few millimeters. This is to ensure that the two microresonators are optically decoupled. As a result, there is no interaction between them, which leads to a common resonance, and manifests itself in a degeneracy, thus leading to line broadening and resolution degradation of the filter.

Both extended surfaces (hereinafter referred to as the first surface and as the opposite second surface of the substrate) have a plane-parallel alignment with each other, the thickness of the substrate is thus constant over the entire usable area. In addition, it is expedient that the surface quality is high in order to avoid scattering effects. Further developments and further embodiments of the inventions are specified in further subclaims.

The invention will be explained in more detail with reference to several embodiments by means of several drawings.

Show it:

1 is a schematic representation in side view of the optical filter element in a general embodiment,

Fig. 2 angle-dependent transmission spectra of microresonators, calculated for a wavelength of 550nm, where

2a shows a resonance layer of silicon dioxide and 100% layer thickness,

2b shows a resonance layer of silicon dioxide and 100.5%

Layer thickness and

Fig. 2c is a resonant layer with four times the thickness of magnesium fluoride and 100% layer thickness

demonstrate, a schematic representation of the functional principle of the directional selection of incident electromagnetic signals by the varying optical geometry along a layer thickness gradient, Figure 4a is a schematic representation of an embodiment of the filter element with additional, direction-limiting wall elements,

4 shows a side view of the exemplary embodiment illustrated in FIG. 4a, showing the functional principle, FIG.

FIG. 5 shows a plurality of transmission spectra of an optical filter element according to FIG. 1, calculated for three angles of incidence, the first surface having a microresonator with titanium dioxide and the second surface having a resonator with magnesium fluoride as central resonant layer, FIG.

Fig. 6 is a schematic representation of the local limitation of the input signal by a variable absorptive or reflective acting prefilter and

7 shows a schematic representation of a spectroscopic / spectrometric device.

In Fig. 1, the structure of an optical filter element 50 is e.g. for a spectroscopic or spectrometric device for the conversion of spectral information into location information schematically sketched.

The optical filter element 50 comprises at least two microresonators 10, 11, wherein a microresonator 10; 11 at least

at least two area-covering reflective layer structures 4, 6; 8, 9 at least from a material layer 2 having a high refractive index and at least one material layer 3 having a low refractive index in an alternating sequence and - At least one area-covering resonance layer 5; 7, between each of the two area-covering reflective layer structures 4, 6; 8, 9 is arranged. According to the invention, the filter element 50 comprises at least

a transparent, plane-parallel substrate 1 for the optical decoupling of the two microresonators 10, 11,

wherein on a first of the two opposite surfaces 51; 52 of the substrate 1, the first microresonator 10; 11 is located

wherein on the substrate 1 on one of the first surface 51 opposite the second surface 54 of the substrate 1, the second microresonator 11; 10, and

the resonant layer 5; 7 at least one microresonator 10, 11 and / or each of the resonant layer 5; 7 surrounding reflective layer structure 4, 6; 8, 9 have a variable layer thickness along a horizontal axis 25 of the filter element 50.

The substrate 1, which is transparent to the spectral region to be analyzed, is provided with plane-parallel, optically smooth surfaces 51 and 52. The thickness h of the substrate 1 in conjunction with the relative thickness gradient of the dielectric layers 2, 3 is a decisive parameter for the directional selectivity or directionality ., the resolution of the filter element 50. On the first surface 51 of the substrate 1 is now on the mutual deposition of dielectric material layers 2 with high refractive index and low-refractive index dielectric material layers 3, a first layer stack 4 generated as a broadband reflector (one-dimensional photonic Crystal) acts. The dielectric first layer stack 4 in FIG. 1 is not of constant thickness but has a continuous layer thickness gradient. The relative difference in thickness between both side surfaces 53 and 54 of the filter element 50 is determined by the requirement for the width of the measuring range. The number of individual alternating layers 2 and 3 determines the resolution of the optical filter element 50. The use of many layers 2 and 3 allows a better separation close to each other Signals, but can negatively affect the sensitivity and also increases the manufacturing requirements.

On the first reflector 4, a resonance layer 5 is now applied, which corresponds in the optical view of a disturbance of the photonic crystal. Typically, their thickness corresponds to a multiple of the thickness of the material layer 2 and the material layer 3. Also in the material layer 2 and the material layer 3, a respective layer gradient is present, which is based on the relative layer thickness profile of the reflector 4.

The first part of the filter element 50 is terminated by a second dielectric reflector 6, as a result of which a so-called microresonator 10 with a locally variable layer thickness and thus continuously changed transmission behavior is produced. As in the case of each resonator, in the microresonator 10 at least one frequency corresponding to the geometry is amplified by multiple reflection and all other portions of the spectrum are suppressed.

The electromagnetic radiation incident on the first part within the measuring range is locally spectrally separated and can penetrate the substrate 1. In order to avoid the problem of the intrinsic dispersion of the microresonator 10, which would make calibration impossible, it is necessary to limit the direction of the signal to be measured. The purpose of the invention is a second microresonator 11 with similar geometry. The second microresonator 11 is likewise composed of a first dielectric mirror 8 and a second dielectric mirror 9 and a resonant layer 7 lying between both mirrors / reflectors 8 and 9.

In the simplest case, the second microresonator 11 is a completely symmetrical image of the first microresonator 10. However, a changed number of layers 2, 3 or material composition or thickness of the resonant layer 5 and 7 is also possible. It is crucial that for a given angle over the entire extent of the filter element 50 there is a match of the resonant wavelength (s). Accordingly, the layer thickness gradients are adapted to each other. FIG. 2 shows angle-dependent transmission spectra of microresonators 10 or 11 calculated for a wavelength of 550 nm, wherein FIG. 2 a shows a resonance layer of silicon dioxide and 100% layer thickness, FIG. 2 b shows a resonance layer of silicon dioxide and 100.5% layer thickness and FIG Fig. 2c shows a resonant layer of four times the thickness of magnesium fluoride and 100% layer thickness.

For this purpose, the typical for three different modeled micro-resonators 10 energetic waveform of a resonant mode (dispersion) is shown. In normal material dispersion, the spectrally narrow (<1 nm FHWM), transparent region shifts with increasing angle of incidence to shorter wavelengths (higher energies) corresponding to ~ M (n d cos (a)). Where n is the refractive index of the material, d is the thickness of the resonant layer 5 and α is the propagation angle.

Real material values are used for the calculation. As an exemplary filter element 50, a dielectric mirror 4 consisting of 550nm / (4n / vfatena /) thick alternating layers 2 and 3 of titanium dioxide and silicon dioxide is adopted. On a glass substrate 1, 7.5 pairs are arranged, followed by the resonant layer 5, and a second dielectric mirror 6 is placed thereon. The thickness of the individual layers 2, 3 corresponds to:

Fig. 2a is 100% of the thickness of 550nm / (4n _Ma teria /), wherein as the resonant layer 5 is a layer of silicon dioxide with a thickness of 550nm / (2ns / fe / _U md / ox ci) is used,

Fig. 2b is 100.5% of the thickness of 550nm / (4n / wateri _a /). wherein as the resonant layer 5, a layer of silicon dioxide with also increased to 100.5% thickness of

Value of 550nml (2n _S Mziumdioxid) is used, and

Fig. 2c 100% of the thickness of 550nm / (4n _Ma fe a /), wherein as the resonant layer 5 a

Layer magnesium fluoride with a thickness of

2- (550nm) ln gnesiumfiuorid _Ma is used.

Despite the very similar course, it can be seen that deviations are present. When comparing the spectrum in Fig. 2a and the spectrum in Fig. 2b the influence of the layer thickness d of the resonance layer 5 on the position of the resonant mode can be recognized. The increase of 0.5% (corresponding to 1 nm of physical thickness) shifts the total dispersion parabola by nearly 3 nm to longer wavelengths. A crossover of the resonance between Fig. 2a and Fig. 2b is given at sufficiently narrow resonant width of both mode (<1 nm) for no angle.

The spectrum in FIG. 2c shows a steeper increase in the associated dispersion parabola resulting from the lower refractive index of magnesium fluoride and the quadrupled layer thickness. If the spectrum in FIG. 2 a is compared with the spectrum in FIG. 2 c, it will be seen that the resonant modes intersect at a low angle and diverge with increasing angle (resonance determined in each case by way of example for 10 °). FIG. 3 shows the operating principle of the directional selection of the filter element 50 introduced in FIG. 1, based on the effects which are listed in the explanation of FIG. Both microresonators 10, 11 have the same gradient and are located opposite one another on the surface of the substrate 1 with a thickness h. A vertically incident signal 12 impinges on the first microresonator 10, and the signal component of the intermediate signal 14 corresponding to 0 ° in FIG. 2a is transmitted and, after passing through the substrate 1, impinges on the second microresonator 11. Since both resonators 5 and 7 are symmetrical, the second microresonator 11 at the entry position of the signal component 14 has the same transmission behavior, thereby the signal component (possibly attenuated) 14 penetrate the second microresonator 11 and detected as an exit signal 14a.

If an inclined incident signal 13 hits the first microresonator 10 at a higher angle, a signal component 15 corresponding to this angle according to FIG. 2 a is transmitted as a resonant mode, the wavelength being smaller in this case than in the case of the vertical incidence of the signal 12 Within the thick substrate 1 compared to the microresonators 10, 11, this mode places a path component L along the layer thickness gradient of the microresonators 10, 11, which results from the substrate thickness h and the angle of incidence of the inclined incident signal 3.

At the entry position to the second microresonator 11, the inclined incident signal 13 now encounters a different layer thickness (thinner or thicker) caused by the gradient. As a result, as explained in the description of Fig. 2, the disperse parabels no longer cross at any point while maintaining the tilt angle, and the signal 15 is reflected as signal 15a instead of transmitted. Decisive for the acceptance angle at which a resonant mode penetrates through both microresonators 10, 11 is the spectral resolution (finesse) of the individual microresonators 10, 11, the thickness h of the substrate 1 and the relative layer thickness gradient.

FIG. 4 a shows an exemplary embodiment of a component 60 with filter element 50, in which it is ensured via highly absorbent wall elements 18, 19 that a directional selection also takes place perpendicularly to the thickness gradient of the microresonators 10, 11. In this direction, the identical geometry ensures that the transmission parabolas of FIG. 2 overlap, thus wavelength calibration would not be possible with tilted incident light of the input signal 13. With the help of the wall elements 18, 19 now an angular range of the input signal 13 is selected. For this purpose, the extent of the filter element 50 is significantly smaller perpendicular to the gradient, as a possible sensor here, for example, line elements are used.

In Fig. 4b, the specific embodiment of the device 60 shown in FIG. 4a is shown in side view to demonstrate the selection of the tilt angle of the incident signal 22. If an input signal 20 falls perpendicularly within the illustrated plane into the component 60 with the filter element 50, then it is not influenced by the wall elements 18, 19 and can subsequently according to FIG. 3 after passing through the microresonators 10, 11 on the back as a signal 25a be detected. An inclined beam 22 at a sufficiently large angle hits one of the wall elements 18, 19 on its way through the component 60 and is absorbed here as a signal 22a. The acceptance angle and, consequently, the spectral resolution of the Filter element 50 within the plane shown is determined by the ratio of wall height and wall distance of the wall elements 18, 19. As a result, a miniaturization of the entire component 60 is possible if the width of the filter element 50 is very narrow perpendicular to the layer gradient. However, the expansion should be a multiple of the average wavelength to be analyzed in order to suppress the influence of diffraction effects while maintaining a sufficiently strong input signal for a high signal-to-noise ratio. FIG. 5 shows, using three calculated transmission spectra for different angles of incidence, an alternative method for the directional selection of the input signal 20 perpendicular to the thickness gradient of the microresonator 10. Shown is a transmitted mode within the otherwise spectrally opaque wavelength range (stop band). The filter element 50 has on its first side a 550nm (2n77 / ancfox _/ d) thick resonant layer 5 of the high refractive index material titanium dioxide (n = 2.1), on the second side a low refractive index microresonator 11 of magnesium fluoride (n = 1.35) with a thickness of (3 × 550 nm) / 2n magnesium fluoride The gradient is symmetrical to the substrate 1, whereby the modes of both microresonators 10 and 11 coincide with normal incidence of light according to FIG. 2a and according to FIG. 2c. As the angle of incidence increases (at 5 ° and 10 °), the resonance shifts to shorter wavelengths, as expected, but at the same time the strength of the signal drops sharply as both parabolas increasingly separate due to the different dispersion.

The spectral resolution is widened in the direction of short wavelengths compared to the transmission under normal incidence of light by this effect, but can continue to be small according to the specific structure of the filter element 50 (<1 nm).

The simulation assumed a _{microresonator} 10 consisting of 7.5 pairs of alternating layers of silicon dioxide and titanium dioxide (thickness of 550nm / (4n _Matef , _a /)), reducing the signal strength, but reducing the effect of angle _selection , thereby reducing spectral resolution. in contrast to the realization of the device 60, as shown in Fig. 4a, 4b, no further elements for confinement of the signal perpendicular to the slice gradient are necessary here. As a result, the component 60 can also be extended over a wide area and is therefore suitable for performing the spectral detection by means of a matrix detector along a spatial coordinate or imaged angular coordinate.

FIG. 6 shows diagrammatically how an input signal 20 in the positions 23, 24, which spectrally exceeds the impermeable wavelength range (stop band), can nevertheless be detected clearly with the presented component 60. At a first position 23 of the input signal 20, the spectrally wide input signal 20 is within the limits of the stopband. Detection may take place after previous passage through the microresonators 10, 11 according to the principles explained in the previous embodiments with intermediate signal 25 and output signal 25a. At a second position 24 of the input signal 20, the spectrally wide input signal 20 exceeds the limit of the stop band, whereby an unambiguous assignment of the detectable signal 25a is no longer possible (either resonant mode or transmitted light outside the stop band). For this reason, an upstream, locally variable filter part 26 suppresses the part of the spectrum which lies outside the respective stop band. The filter part 26 can act both absorptively (for example: functional dyes), as well as reflective (bandpass filter). For the local arrangement of the filter part 26 discrete steps as well as layer gradient curves are possible.

FIG. 7 shows a spectroscopic / spectrometric device 70 for converting spectral information into location information, which comprises at least

a light source 16,

a detector 30,

an evaluation unit 40, which is connected via a connecting line 35 to the detector 30,

a display unit 17 and an aforementioned filter element 50 according to the invention,

wherein the filter element 50 is formed such

that it transmits a short-wave component 32b of the light from the light source 16 after passing through the filter element 50 in the short-wave transparent region and a long-wave component 33b of the light from the light source 16 after passing through the filter element 50 in the long-wave transparent region

such as

that it reflects a long-wave component 31b of the light of the light source 16 after hitting the filter element 50 in the short-wave transparent region and a short-wave component 34b of the light of the light source 16 after hitting the filter element 50 in the long-wave transparent region.

In Fig. 7 the following light components are given

a long-wave component 31a of the light of the light source 16 before impinging on the filter element 50 in the short-wave transparent region,

a long-wave component 31 b of the light of the light source 16 after striking the filter element 50 in the entertaining transparent region,

a short-wave component 32a of the light of the light source 16 before passing through the filter element 50 in the short-wave transparent region,

a short-wave component 32b of the light of the light source 16 after passing through the filter element 50 in the short-wave transparent region,

a long-wave component 33a of the light of the light source 16 before passing through the filter element 50 in the long-wave transparent region,

a long-wave component 33b of the light of the light source 16 after passing through the filter element 50 in the long-wave transparent region,

a short-wave component 34a of the light of the light source 16 before hitting the filter element 50 in the long-wave transparent region and

a short-wave component 34b of the light of the light source 16 after hitting the filter element 50 in the long-wave transparent region.

The advantages of the filter element 50 according to the invention for a spectrometer 70 consist of the following: The construction according to the invention makes it possible to realize particularly space-saving spectrometers 70 in the direction of propagation of the light signal, since the size of the spectrometer 70 is defined only with a minimum vertical distance between the filter element 50 and the detector 30 according to FIG.

If a two-dimensional element (matrix) is used for the detector 30, depending on the optical configuration on the input side, on the one hand the signal quality can be increased (integration), or a location-dependent / angle-dependent spectral measurement can be performed.

Through the use of dielectric materials, a high sensitivity (transmission of the resonance near 100%) with simultaneously high selectivity (narrow half-width of the signal) and favorable SNR (spectral environment of the resonance with transmission <0.1%) can be achieved. By selecting the lateral extent of the filter element-detector combination and the density of the detector elements, it is additionally possible to influence the resolution of the spectrometer.

The use of non-uniform layer thickness curves allows the production of specific spectrometers with different measuring ranges in one device (for example: rough spectral overview and finely resolved section). In addition, the basic structure can be easily encapsulated and used because of the small number of necessary components in particularly stressed environments.

Furthermore, the components, such as high-resolution detectors 30, are now mass-produced and the filter elements 50 can be produced in parallel in larger quantities, so that the total cost of a spectrometer 70 with the optical filter element 50 according to the invention can be low. LIST OF REFERENCE NUMBERS

1 substrate

2 material layer high refractive index

3 material layer of low refractive index

4 first layer stack / first reflector

5 first resonant layer

6 second layer stack / second reflector

7 second resonant layer

8 layer stack / reflector

9 layer stack / reflector

10 first microresonator

11 second microresonator

12 incoming signal

13 input signal

14 intermediate signal

14a exit signal

15 reflective signal component

15a transmissive signal component

16 light source

17 display unit

18 first wall element

19 second wall element

20 input signal

21 horizontal axis of the filter element

22 inclined incident signal

22a absorbed signal

23 position

24 position

25 intermediate signal

25a exit signal

26 filter part

30 detector

31a Long wave component of the light before hitting the filter element in shortwave transparent area

31 b Long-wave component of the light after hitting the filter element in the short-wave transparent area

32a Short-wave component of the light before passing through the filter element in the short-wave transparent region

32b Shortwave contribution of light after passing through the

Filter element in the short-wave transparent area

33a Long-wave component of the light before passing through the filter element in the long-wave transparent region

33b Long-wave component of the light after passing through the

Filter element in the long-wave transparent area

34a short-wave component of the light before hitting the filter element in the long-wave transparent region

34b Short-wave component of the light after hitting the filter element in the long-wave transparent region

35 connecting line

40 evaluation unit

50 filter element for converting spectral information into one

location information

51 first surface

52 second surface

53 first filter element side

54 second filter element side

60 component

70 spectroscopic device h Thickness of the substrate

d thickness of the resonator layer

a propagation angle

n refractive index

Claims

claims

1. An optical filter element (50) for devices (70) for converting spectral information into location information with an activated detector (30) for detecting signals,

at least comprising two microresonators (10, 11),

wherein a microresonator (10; 11) at least comprises

- At least two area-covering reflective layer structures (4, 6;

8, 9) at least one material layer (2) with a high refractive index and at least one material layer (3) with a low refractive index in an alternating sequence and

at least one surface-covering resonance layer (5, 7) which is arranged between the respective two surface-covering reflective layer structures (4, 6, 8, 9),

characterized,

in that the filter element (50) at least comprises

a transparent, plane-parallel substrate (1) for the optical decoupling of the two microresonators (10, 11),

wherein the first microresonator (10; 11) is located on a first of the two opposite surfaces (51; 52) of the substrate (1), wherein on the substrate (1) on a second opposite one of the first surface (51) Surface (54) of the substrate (1) of the second microresonator (11; 10) is located, and

wherein the resonant layer (5; 7) of at least one microresonator (10; 11) and / or the respective reflective layer structure (4,6; 8,9) surrounding the resonant layer (5; 7) has a variable layer thickness along a horizontal axis (25). of the filter element (50).

2. An optical filter element according to claim 1,

characterized,

in that at least a portion of the reflective layer structure (4, 6, 8, 9) and / or at least one resonance layer (5, 7) is made of a dielectric material Material exist.

3. An optical filter element according to claim 1,

characterized,

in that at least one of the reflective layer structures (4, 6; 8, 9) consists of a layer stack of alternating high-index and low-refractive optically transparent materials.

4. Optical filter element according to claims 1 to 3 ,,

characterized,

in that at least one resonant mode of the microresonators (10, 11) has a transmittance higher than 10%, preferably higher than 50%, particularly preferably higher than 90%.

5. An optical filter element according to claims 1 to 4,

characterized,

that the geometric structure and / or the material composition of both microresonators (10, 11) are symmetrical to the substrate plane.

6. An optical filter element according to claim 1,

characterized,

in the case of the filter element (50), the profile of the layer thicknesses of the reflective layers (2, 3) along a horizontal axis (21) of the component (60) or filter element (50) has a relation to the course of the resonance layer thickness.

7. An optical filter element according to claim 1,

characterized,

the first resonant layer (5) of the first microresonator (10) consists of a dielectric material different from the second resonant layer (7) of the second microresonator (11), and thus the resonant mode (s) comprise a dispersion parabola having mutually different curvatures. owns gene (s).

8. An optical filter element according to claim 1,

characterized,

the extent of the surface (51, 52) of the substrate (1) perpendicular to the slice gradient direction is relatively small.

9. An optical filter element according to claim 1,

characterized,

that in the direction of irradiation elongated, absorptive wall elements (18, 19) on the sides (53, 54) of the filter element (5) are mounted.

10. An optical filter element according to claim 1 '

characterized,

in that a locally variable optical filter part (26) is mounted in front of the one of the micro-sensors (10, 11) in which a spectral preselection of an incoming signal (20) takes place through absorptive, transmissive or reflective bandpasses.

11. Spectroscopic / spectrometric means (70) for converting spectral information into location information, at least comprising

a light source (16),

a detector (30),

an evaluation unit (40) which is connected to the detector (30) via a connecting line (35),

a display unit (17) and

a filter element (50) according to claims 1 to 10,

characterized,

the filter element (50) is designed in such a way

that a short-wave component (32b) of the light from the light source (16) after passing through the filter element (50) in the short-wave transparent region and a long-wave component (33b) of the light from the light source source (16) after passing through the filter element (50) passes in the long-wave transparent region and

in that there is a long-wave component (31b) of the light from the light source (16) after hitting the filter element (50) in the short-wave transparent region and a short-wave component (34b) of the light from the light source (16) after hitting the filter element (50 ) is reflected in the long-wave transparent region.

12. Spectroscopic / spectrometric device according to claim 11,

characterized,

in that it has a photoelectric series / matrix converter on the basis of CCD, photodiode or multiplier as the detector (30).